your purchase could not be completed

If you are also getting a message to contact iTunes Support then to do so (these are user-to-user forums) :

- go to http://www.apple.com/support/itunes/ww

- click on your country's flag

- click on the Contact Support at the bottom of the left-hand column

- click on Contact iTunes Store Support on the right-hand side of the page

- then Purchases, Billing & Redemption